1. Field of the Invention
The present invention relates to a spindle structure in an ultrasonic machine which can perform grinding work, cutting work or the like on a workpiece with a high degree of accuracy and efficiency while applying ultrasonic vibration to various working tools.
2. Description of the Related Art
In a field of precision working of a member to be difficult to be worked, such as a highly hard brittle material, a metal composite material or the like, an ultrasonic machine is used as cutting working or boring working means. The ultrasonic machine is generally provided with a spindle rotationally driven by a motor, an ultrasonic vibrator arranged coaxially to the spindle, a horn connected to the ultrasonic vibrator integrally therewith, and a working tool, such as a cutting tool, a grinding tool or the like, which is mounted on the tip end of the horn, in which an ultrasonic vibration system is fixed in a high-rigid state.
In such an ultrasonic machine, in order to maintain preciseness capable of precision working, it is necessary to maintain the assembling precision of the spindle, the ultrasonic vibrator and the horn in a severe and high-rigid state. In addition, the most important object in designing is to make ultrasonic vibration applied by the ultrasonic vibrator completely coincide with the axial direction and to transmit the vibration to a machining tool with a constant amplitude of the vibration.
The present applicant has developed a spindle structure in an ultrasonic machining where ultrasonic vibration can be transmitted to a working tool for cutting work or grinding work without wobbling around a rotating shaft and with high efficiency, and cutting work or grinding work can be performed with extreme accuracy, and such a spindle structure has been disclosed in Unexamined Japanese Patent Publication No. 2000-254801.
FIG. 9 is a partial sectional view showing a spindle structure of an ultrasonic machine disclosed in the above publication. As shown in FIG. 9, the spindle structure is provided with a spindle 63 rotationally driven around an axial line thereof, an ultrasonic vibrator 64 housed in a hollow main body sleeve 63b formed in the spindle 63, two supporting horns 66, 67 connected coaxially to the ultrasonic vibrator 64 and fixed to an inner peripheral wall of the main body sleeve 63b in a constraining manner, a holder horn 65 whose proximal end is connected coaxially to the supporting horns 66, 67 and whose distal end is attachable to a cutting tool 68, and the like.
Also, the supporting horns 66, 67 comprise main bodies 66a, 67a arranged coaxially to the ultrasonic vibrator 64, base portions 66c, 67c integrally formed at intermediate portions, in axial directions, of the main bodies 66a, 67a, elastically deformable cylindrical thin damping sleeves 66d, 67d formed coaxially to the base portions 66c, 67c around the main bodies 66a, 67a, and flanges 66e, 66f, 67e, 67f formed on both ends of the damping sleeves 66d, 67d in their axial directions.
These supporting horns 66, 67 are provided inside the main body sleeve 63b of the spindle 63 in a state where they have close contact to each other, and the flanges 66e, 66f, 67e, 67f are fixed into the inner peripheral wall of the main body sleeve 63b. A spacer member (not shown) may be disposed between the flanges 66e and 66f, 66f and 67e, and 67e and 67f, respectively.
By employing such a spindle structure, ultrasonic vibration transmitted from the ultrasonic vibrator 64 to the main bodies 66a, 67a of the supporting horns 66, 67 are transmitted to the holder horn 65 side as they are. On the other hand, since the transmission to the spindle 63 is buffered by the damping sleeves 66d, 67d, the leak of ultrasonic vibration energy to the spindle 63 is suppressed. Thus the vibration transmission rate to the holder horn 65 can be kept high, while working accuracy can be significantly improved by maintaining the spindle 63, which is a main rotation shaft, and the holder horn 65 on the same axis.
In the spindle structure shown in FIG. 9, it is necessary to arrange, inside the main body sleeve 63b, the members such as the supporting horns 66, 67 and the spacers (not shown) in a state where they have close contact to each other without any gap therebetween, thereby restraining the members in both axial and peripheral directions of the spindle 63. In addition, the members should be assembled so as not to introduce any strain or concentrated stress on any member. Therefore, during the assembly process, it is necessary to precisely adjust the position and attitude of the respective members with the utmost care by watching to confirm that there is no gap between adjacent members upon every assembly of one member. This requires not only the skill and technique of the worker but also a vast number of assembling steps. Moreover, since a plurality of supporting horns, that is, the supporting horns 66, 67, are arranged to be in close contact with each other, core wobbling after assembly due to uneven size accuracy of the members cannot be avoided even when the members have been assembled with great care, which leads to poor machining accuracy.
Additionally, since the flanges 66e, 66f, 67e, 67f of the supporting horns 66, 67 are fixed into the inner peripheral wall of the main body sleeve 63b, a part of the ultrasonic vibration transmitted from the ultrasonic vibrator 64 to the main body 66a, 67a of the supporting horns 66, 67 may leak through the members such as the flanges 66e, 66f, 67e, 67f to the main body sleeve 63b to generate heat. In this regard, owing to the relatively large total length of the members such as the supporting horns 66, 67 coaxially connected, any deformation by the heat generation increases and, therefore, easily causing rolling of the cutting tool 68, which results in degradation of machining accuracy.
An object of the present invention is to provide a spindle structure of an ultrasonic machine capable of reducing the number of assembling steps and improving machining accuracy as well as a supporting horn used in the same.
A spindle structure of an ultrasonic machine according to the present invention comprises a spindle main body rotationally driven around an axial line thereof, an ultrasonic vibrator housed in a cylindrical main body sleeve formed in the spindle main body, and a supporting horn connected to the ultrasonic vibrator within the main body sleeve, wherein the supporting horn comprises a main body connected coaxially to the ultrasonic vibrator, a base portion formed in a brim shape on an outer peripheral face of the main body, an elastic cylindrical damping sleeve formed by extending an outer periphery of the base portion in the axial direction, a loose flange formed on one end of the damping sleeve, a fixing flange formed on the other end of the damping sleeve, and a gap portion formed on an outer peripheral face of the base portion along a circumferential direction thereof, the loose flange of the supporting horn being disposed on the side of the ultrasonic vibrator in a state that the loose flange is slidable to and has contact with an inner peripheral face of the main body sleeve and the fixing flange being mounted on the main body sleeve in such a state that the fixing flange is restrained in the axial direction. Here, the term xe2x80x9cloose flangexe2x80x9d means a flange which is restrained only in a diametrical direction by making an outer peripheral portion of the flange abut another member, and the term xe2x80x9cfixing flangexe2x80x9d means a flange which is restrained at least in the axial direction by making a face of the flange crossing in its axial direction abut another member. The term xe2x80x9cgap portionxe2x80x9d means a portion where continuity of an outer peripheral face is interrupted, for example, a portion where a hole, a groove, a slit or the like is formed.
The loose flange of the supporting horn is disposed on the side of the ultrasonic vibrator in a state that it is slidable to and has contact with the inner peripheral face of the main body sleeve and the fixing flange is fixed to the main body sleeve in a state where it is restrained in the axial direction, so that the supporting horn is restrained in the axial direction at the position of the fixing flange while the supporting horn is restrained in the diametrical direction but not restrained in the axial direction at the position of the loose flange. Therefore, the supporting horn main body allows efficient transmission of ultrasonic vibration applied from the ultrasonic vibrator in the axial direction by stretching/retracting motion of the supporting horn main body itself utilizing the fixing flange portion as a fulcrum. Also, since the gap portion is provided on the outer peripheral face of the base portion of the supporting horn along the circumferential direction, each of the loose flange and the fixing flange of the damping sleeve is easily deformed independently from the supporting horn main body, so that ultrasonic waves applied to the supporting horn main body is prevented from leaking to the main body sleeve through the loose flange and the fixing flange.
In other words, ultrasonic waves applied from the ultrasonic vibrator to the supporting horn can be transmitted to a working tool without leaking, thereby preventing heat generation caused by the ultrasonic wave leakage during the working process. This also eliminates rolling caused by minute deformation of the supporting horn due to heat generation, which leads to better working accuracy. In addition, since only the fixing flange is fixed to the main body sleeve, a spacer or the like is not required. As a result, the number of members is reduced and a strict adjustment is not required when assembling, so that the number of assembling steps can be remarkably decreased. Moreover, heat generation due to the ultrasonic waves leaking from the flange through a spacer can be prevented.
Here, as the gap portion of the supporting horn, provided is a buffer groove extending in a circumferential direction on an outer peripheral face of the base portion. Thus, the damping sleeve on the loose flange side and the damping sleeve on the fixing flange side are being separated in the axial direction by the buffer groove extending in the circumferential direction, so that both sides of the damping sleeve can be more easily deformed independently. Accordingly, a function preventing leakage of ultrasonic waves applied to the main body to the main body sleeve is further enhanced so that heat generation due to ultrasonic wave leakage during working process can be remarkably reduced.
Here, it is preferable that the length, in the axial direction, of the main body of the supporting horn is set to be xc2xd of the wavelength of an ultrasonic wave applied, the length, in the axial direction, of the damping sleeve of the supporting horn is set to be within xc2xc of the wavelength of an ultrasonic wave applied, and the base portion is formed in an intermediate position of the main body in the axial direction and in an intermediate position of the damping sleeve in the axial direction. By this structure, the main body of the supporting horn, while efficiently vibrating itself with ultrasonic waves applied to the main body, can transmit the ultrasonic waves to the holder horn or the like. Thus, not only the working process becomes faster, leading to improved working efficiency, but also a function of preventing ultrasonic waves from leaking to the main body sleeve is enhanced, so that heat generation due to ultrasonic wave leakage during the working process can be suppressed to the minimum.
Furthermore, by setting the width of the buffer groove in a range of 0.1% to 3% of the wavelength of an ultrasonic wave applied, an excellent ultrasonic wave transmitting function and an excellent ultrasonic wave leakage preventing function are exhibited while maintaining the strength of the supporting horn, so that higher reliability and durability can be achieved while maintaining the working process efficiency at a high level.
By providing a portion where the outer diameter of the main body of the supporting horn varies continuously or intermittently along the axial direction of the main body within a range of the inner diameter of the damping sleeve, an amplifying-type supporting horn where the entire shape of the main body is gradually reduced in diameter from the ultrasonic vibrator side towards the holder horn side or a damping-type supporting horn where the entire shape is gradually increased in diameter towards the holder horn side is obtained. In either case, an excellent ultrasonic wave transmitting function and an excellent ultrasonic wave leakage preventing function can be exhibited, so that improvement in working accuracy and reduction in heat generation due to ultrasonic wave leakage during working process can be achieved.
Next, a supporting horn according to the present invention is a supporting horn which is connected to an ultrasonic vibrator disposed inside a spindle main body of an ultrasonic machine, the supporting horn comprising a main body connected coaxially to the ultrasonic vibrator, a base portion formed in a brim shape on an outer peripheral face of the main body, an elastic cylindrical damping sleeve formed by extending an outer peripheral portion of the base portion in the axial direction, a loose flange formed on one end of the damping sleeve, a fixing flange formed on the other end of the damping sleeve, and a gap portion provided along a circumferential direction on an outer peripheral face of the base portion.
By disposing the supporting horn on the side of the ultrasonic vibrator in a state where the loose flange of the supporting horn is slidable to and has contact with an inner peripheral face of the cylindrical main body sleeve provided inside the spindle main body of the ultrasonic machine and fixing the supporting horn to the main body sleeve in a state where the fixing flange is restrained in the axial direction, the supporting horn is restrained in the axial direction at the position of the fixing flange portion while the supporting horn is restrained in the diametrical direction but not restrained in the axial direction at the position of the loose flange. Therefore, the supporting horn main body allows efficient transmission of ultrasonic vibration applied from the ultrasonic vibrator in the axial direction by stretching/retracting motion of the supporting horn main body itself. Also, by providing the gap portion, each loose flange and fixing flange of the damping sleeve is easily deformed independently from the supporting horn main body, so that ultrasonic waves applied to the supporting horn main body is prevented from leaking to the main body sleeve through the loose flange and the fixing flange.
As described above, since it becomes possible to transmit ultrasonic waves applied from the ultrasonic vibrator to the holder horn and the like without wasting, heat generation due to ultrasonic wave leakage during working process can be remarkably reduced, thereby improving the working accuracy. In addition, since only the fixing flange is fixed to the main body sleeve, a spacer or the like is not required. As a result, the number of members is reduced and a strict adjustment is not required when assembling, so that the number of assembling steps can be remarkably decreased. Moreover, heat generation caused by fixing a spacer to the flange without any gap therebetween, which was a problem in the conventional structure, can be prevented.
Here, as the gap portion, provided is a buffer groove extending in a circumferential direction on an outer peripheral face of the base portion. Thus, the damping sleeve on the loose flange side and the damping sleeve on the fixing flange side are being separated in the axial direction by the buffer groove extending in the circumferential direction, so that both sides of the damping sleeve can be more easily deformed independently. Accordingly, a function preventing leakage of ultrasonic waves applied to the main body to the main body sleeve is further enhanced.
By setting the length, in the axial direction, of the main body of the supporting horn to xc2xd of the wavelength of an ultrasonic wave applied, setting the length, in the axial direction, of the damping sleeve of the supporting horn to within xc2xc of the wavelength of an ultrasonic wave applied, and forming the base portion in an intermediate position of the main body in the axial direction and in an intermediate position of the damping sleeve in the axial direction, the main body of the supporting horn, while efficiently vibrating itself with ultrasonic waves applied to the main body, can transmit the ultrasonic waves to the holder horn or the like. Thus a function of preventing ultrasonic waves from leaking to the main body sleeve is enhanced.
By setting the width of the buffer groove in a range of 0.1% to 3% of the wavelength of an ultrasonic wave applied, an excellent ultrasonic wave transmitting function and an excellent ultrasonic wave leakage preventing function are exhibited while maintaining the strength of the supporting horn.
By providing a portion where the outer diameter of the main body of the supporting horn varies continuously or intermittently along the axial direction of the main body within a range of the inner diameter of the damping sleeve, an amplifying-type supporting horn where the entire shape of the main body is gradually reduced in diameter from the ultrasonic vibrator side towards the holder horn side or a damping type supporting horn where the entire shape is gradually increased in diameter towards the holder horn side is obtained. In either case, an excellent ultrasonic wave function and an excellent ultrasonic wave leakage preventing function can be exhibited.